Project Summary/Abstract The objective of this pilot proposal is to identify patterns of body mass index (BMI) change in Veterans returning from Afghanistan (Operation Enduring Freedom) and from Iraq (Operation Iraqi Freedom). We will create and analyze a longitudinal database, using VA electronic record data from the Women Veterans Cohort Study (WVCS HSR&D funded). The study sample will include OEF/OIF Veterans who have 1) a VA encounter within one year of end date of last deployment with height, weight, and pain rating available from vital signs data, and, and 2) a minimum of three additional encounters at least six months apart with weight and pain data between 2001 - 2007. Demographic, military service, physical and mental health, pharmaceutical, and utilization data will also be extracted. During the pilot study year, latent growth mixture modeling analyses will be conducted to identify discrete BMI trajectories. Our Pilot Study Specific Aims are to 1) determine distinct BMI trajectories in returning OEF/OIF Veterans beginning at first year post-deployment and 2) examine distinct BMI trajectories in OEF/OIF female and male Veterans, and by race. Within each sample, we will identify the optimal number of trajectory classes that will best fit the data and the distinctive patterns of BMI change. This preliminary work will be the basis of the larger study that will identify demographic, military service, pain, health, and utilization data factors associated with individual BMI trajectory group membership. We will examine how distinctive patterns of BMI change differ from each other in predictable ways and identify factors within the Veteran population associated with weight gain, weight maintenance and weight loss. Our goal is to assist VA in identifying risk periods for weight change and critical time points for intervention that will facilitate the development of tailored strategies targeted at promoting successful weight maintenance and preventing weight gain.